With development of magnetic field sensor technologies, magnetic field sensors have developed from early single-axis magnetic field sensors to later double-axis magnetic field sensors and then to current three-axis magnetic field sensors, such that they can detect magnetic field signals in three directions of X, Y and Z axes in the space comprehensively. For magnetic field sensors such as AMR, Giant Magnetoresistive (GMR) and Tunneling Magnetoresistive (TMR), a magnetic field sensing direction is in a film plane, and measurement on X-axis and Y-axis magnetic field components in the plane may be implemented by making two sensors orthogonal, thereby implementing an XY two-axis magnetic field test system. However, for a Z-axis magnetic field component, a solution is erecting a discrete single-axis plane magnetic field sensor on a two-axis plane sensor, for example, a three-axis magnetic field sensor disclosed in the patent with Application No. 201110251902.9 and entitled “Three-Axis Magnetic Field Sensor”. However, this method has the following defects:
1) The X, Y two-axis magnetic field sensor and the Z single-axis magnetic field sensor are discrete elements before mounting, so that integrated manufacture of the three-axis magnetic field sensor cannot be implemented, thereby increasing the complexity of the manufacturing process.
2) Compared with an integrated manufacturing system, position precisions of elements in a three-axis magnetic field sensor system manufactured by assembling are reduced, thus affecting the measurement precision of the sensor.
3) A sensing axis of the Z single-axis magnetic field sensor is perpendicular to the X, Y two-axis magnetic field sensor, and therefore, the dimension of the three-axis magnetic field sensor in the Z direction is increased, thereby increasing the device size and the difficulty in packaging.
Another solution is using a slope to set a magnetic field sensor unit to detect a magnetic signal in the Z direction, as disclosed in the patent CN202548308U entitled “Three-Axis Magnetic Field Sensor”. However, an angle of forming the slope in the sensor in this structure is hard to control, and shadowing effects are likely to be caused in the process of depositing a magnetoresistive film on the slope, thereby reducing the performance of a magnetic field sensor element. Moreover, an algorithm is needed to calculate a magnetic signal in the Z-axis direction.
Another solution is a solution disclosed in the patent application 201310202801.1 entitled “A Three-Axis Digital Compass”, which converts a Z-axis magnetic field component perpendicular to a plane into a magnetic field component in an XY plane by using a distortion function of a flux concentrator on the magnetic field, thereby implementing measurement on a magnetic signal in a Z-axis direction. However, the magnetic field sensor in this structure needs an Application-Specific Integrated Circuit (ASIC) chip or computation using an algorithm to obtain magnetic signals in three directions of the X, Y and Z axes.
Currently, a three-axis magnetic field sensor is manufactured mainly by methods such as etching a substrate layer of a substrate to form a slope, depositing a magnetoresistive material film on the slope and double deposition, for example, a manufacturing process of a sensor disclosed in the patent CN202548308U entitled “Three-Axis Magnetic Field Sensor” substantially comprises etching a substrate layer of a wafer to form two slopes, double-depositing a magnetoresistive material film on the two slopes respectively, and conducting double annealing to manufacture sensor units in an XZ direction and a YZ direction. The European Patent Application EP 2267470 B1 also discloses a method for manufacturing a three-axis sensor, in which a substrate is etched to form a slope, and a sensor unit for measuring a magnetic field component in a Z-axis direction is manufactured on the slope. Grades of the etched slopes in the two patent applications are hard to control, and there is difficulty in depositing the magnetoresistive material film on the slope, which are not conducive to actual implementation.